1. Field of the Invention
This invention relates to soft tissue anchoring devices for securing ligament or tendon to bone. This invention also relates to an installation tool and method for inserting the anchoring device into bone.
2. Description of the Related Art
There are a variety of methods for soft tissue attachment to bone. The oldest technique requires holes to be made through bone. The suture is passed through the holes and is used to tie the soft tissue to the bone. This method is still used today in older osteoarthritic patients, but it is considered difficult and time consuming with increased trauma to the patient.
Other methods involve using soft tissue anchoring devices. Several approaches to stapling or tacking soft tissue to bone have been used. An example of a staple device is disclosed in U.S. Pat. No. 4,873,637. This teaches a staple device having two or more leg portions and a body disposed between the legs. An example of a tacking device is taught in U.S. Pat. No. 4,873,976. It teaches a nail with multiple barbs and a tissue retaining head. Drawbacks of these types of devices are that they are relatively large and require anchor sites of greater bone stock which limits their application. They can also can break or split bone on their deployment.
Other soft tissue anchoring devices are composed of an anchor and a surgical suture. The anchor is installed in the bone. Then the suture is passed through the soft tissue and tied to the bone surface. Examples of these devices are taught in U.S. Pat. No. 5,013,316 which describes a metallic threaded suture anchor and U.S. Pat. No. 5,046,513 which describes a metallic anchor with elastic barbs. Drawbacks of these devices include anchor loosening and migration, patient sensitivity to nickel, corrosion of metals and interference with imaging techniques such as MRI.
U.S. Pat. No. 5,690,678 teaches the use of a slot and subsurface channel machined into bone. Suture is anchored to the bone with knots or beads. Orientation of the slot is critical in this system. If mechanical forces move the knot or bead to the introduction hole, the suture can become dislodged from the bone. U.S. Pat. No. 5,569,303 also discloses anchors deployed in a slot machined in bone. The anchor is inserted with its long axis parallel with the bone surface and rotated about the short axis of the anchor. A slot machined in bone as described in both of the above patents, creates a large defect in bone in comparison to devices installed perpendicular to the bone surface. The larger the defect, the greater the risk to the structural integrity of the surrounding bone. This limits the application of this device to good quality bone only. Also, a machined slot can allow for increased movement of the sutures along the machined bone surfaces. This can abrade and weaken the suture which can lead to premature failure.
Suture anchors can also be fabricated of bioabsorbable materials which are absorbed over time in the body and replaced by bone. This may reduce the possibility of joint damage due to anchor loosening and migration. Also, bioabsorbable polymers do not interfere with imaging techniques such as MRI. Examples of these devices are taught in U.S. Pat. No. 5,573,548 which teaches a bioabsorbable threaded suture anchor and U.S. Pat. No. 5,584,836 which describes a threaded, cannulated absorbable suture anchor. These devices offer advantages because they are made of absorbable polymer. This feature also means that they lack the hardness to be self tapping as in metal anchors. Consequently bioabsorbable suture anchors with screw threads require increased site preparation. Drilling and tapping threads into bone must be completed prior to installation of the anchor.
The primary object of this invention is to provide an improved soft tissue anchor which is mechanically stable, easy to manufacture, use and install.
Another object of the present invention is to provide an improved bone boring tool wherein the tool is used to create a non-circular shaped hole in bone approximating the cross section of the anchoring device.
Still another object of this invention is to provide a novel method for deploying the soft tissue anchor in bone.